I just noticed this today. When I tried to activate AP and it failed to do so, I got the shrill 3 chime warning one typically hears when say... opening a door when in drive. Now, this is different from what I remeber, as the failed chime used to be the same "AP engaged" chime but in reverse order (higher pitched to lower pitched versus lower to higher pitched chime tones). This is actually really good news, as this audio cue is much more noticeable! I'm not exactly sure when this change came about, so I'm wondering when other people noticed this... anyone? Bueler?